Clutch for a power train of a motor vehicle

ABSTRACT

A motor vehicle clutch has at least one flywheel ( 4   a ) equipped with fan blades ( 34 ) at least in a zone that is radially between a hub ( 54 ) and a solid ring portion with a friction surface ( 48 ). The clutch is configured so that the fan blades of the rotating flywheel will generate an air stream to flow over the surface portion of the flywheel on the opposite side from the friction surface for efficient cooling of the clutch.

BACKGROUND OF THE INVENTION

The invention relates to a clutch, in particular for a power train of amotor vehicle. The clutch has an input shaft supporting a flywheel witha substantially ring-shaped friction surface and an output shaftsupporting a clutch disc with a friction lining conforming to thefriction surface of the flywheel. The flywheel is constrained to rotatetogether with the input shaft, and the clutch disc is constrained torotate with the output shaft. The clutch further has an axially movablepressure plate and an actuator device that serves to move the pressureplate and thereby engage and disengage the clutch. In the engagedposition, the pressure plate is urging the clutch disc intofriction-locked compressive contact against the flywheel. In thedisengaged position, the pressure plate is retracted, whereby thefriction-lock between the input shaft and the output shaft isinterrupted. The aforementioned components are enclosed in a housingwith openings for the input shaft and the output shaft to pass through.

FIG. 5 provides a general orientation of the layout and function of amotor vehicle clutch. An input shaft 2 originating from a source ofmotive power, e.g., the crankshaft of an engine, carries a flywheel 4that is constrained on the input shaft to share its rotation. Theflywheel 4, which generally performs the function of an engine flywheel,extends as a disc from the input shaft to an outer circumference whereits contour turns into the axial direction to form a cylindrical wall,ending in a radially inward bent rim that forms an abutment ring 6.Running axially in line with the input shaft 2 is an output shaft 8. Aclutch disc 10 is attached to the output shaft through a rotationallyfixed connection. The radially outer portion of the clutch disc 10carries a substantially ring-shaped friction lining 12 designed toengage a corresponding friction surface of the flywheel 4. The flywheel4 can likewise be equipped with a friction lining.

The clutch disc 10 is axially movable in relation to the output shaft 8,or flexibly deformable in the axial direction. A pressure disc orpressure plate 14 that is axially movable in relation to the outputshaft 8 and can be rotationally constrained to the latter serves topress the clutch disc 10 against the flywheel 4. Normally, a diaphragmspring 16, seated at its outer circumference against the abutment ring6, pushes the pressure plate 14 against the clutch disc 10, so that thelatter is in non-slipping frictional engagement with the flywheel 4. Theradially inner border of the diaphragm spring is held in a retractingring 18 that is rotatably supported on an actuator ring 20. The actuatorring 20 is axially movable on the output shaft 8 by means of an actuatormechanism 22. By moving the actuator ring 20 to the right (as shown inFIG. 5) the diaphragm spring 16 is caused to change its shape so thatthe pressure plate 14 is no longer pushed against the clutch disc 10 andthe clutch is taken out of engagement. The entire arrangement isaccommodated in a housing 24 that is formed by a so-called clutch bell26 and the engine housing 28. The clutch bell 26, covering the side ofthe clutch facing towards the transmission, is attached to the enginehousing 28.

Mechanical clutches of this kind, which include one or more flywheels,have to meet exacting requirements. The clutch is expected to engagesoftly, to transmit large amounts of torque, and to have a longoperational life span. If the clutch is used in conjunction withautomated shift transmissions, in particular with transmissions thatshift under load, where several gear shifts can occur in rapidsuccession under a high torque load, large amounts of heat may begenerated in the clutch, which can be detrimental to its functionalityand shorten its useful life.

OBJECT OF THE INVENTION

It is therefore the object of the present invention to further develop aclutch of the kind described above in order to increase the rate atwhich the clutch can convert mechanical energy into thermal energywithout suffering damage.

SUMMARY OF THE INVENTION

According to the invention, the foregoing objective is met by a clutchin which the flywheel has fan blades arranged at least in a zone that isradially inside the friction surface, so that the rotation of theflywheel will cause an air stream to flow over the side of the flywheelthat faces away from the friction surface.

In a clutch designed in accordance with the invention, the air streamwill carry the heat away significantly faster, so that even at a highrate of heat generation, the friction linings will remain at a lowtemperature and will therefore not be exposed to the risk of beingdamaged.

In a preferred embodiment of the invention, the flywheel, the clutchdisc and the pressure plate have air passages located in a radial zonebetween the output shaft and the friction lining. This allows the airstream generated by the fan blades of the flywheel to flow axially alongthe output shaft.

Also preferred according to the invention is a configuration of theclutch where the housing surrounds the flywheel, the clutch disc and thepressure plate at a sufficient distance for the air to circulate in aclosed loop. Passing through the aforementioned air passages in theflywheel, the clutch disc and the pressure plate, the air will move inan axial direction along the output shaft from the pressure plate to theflywheel, then turn radially outwards and continue its circulation pathbetween the housing and the flywheel, then turn into the axial directionalong the peripheral housing wall from the flywheel to the pressureplate, and finally turn back inwards in the radial direction to completethe loop of air circulation.

In another preferred embodiment of the invention, the housing has an airinlet and an air outlet. In this case, outside air enters the housingthrough the inlet, then flows on a path inside the housing that leadsthrough the flywheel, and leaves the housing through the air outlet.

In the embodiment of the preceding paragraph, a preferred location forthe air inlet is on the side of the housing that is farther away fromthe flywheel, while the air outlet is located preferably in a peripheralhousing wall, so that the air flow path runs in an axial direction fromthe air inlet along the output shaft, passes through the flywheel, thenturns into an outward radial direction between the housing and theflywheel and exits from the housing through the air outlet.

In a clutch according to the invention, it is advantageous if thehousing has an interior surface that is provided with cooling fins.

In clutches according to the invention, it is preferred if the flywheelperforms the function of an engine flywheel.

In preferred embodiments of the invention, it is of advantage if theflywheel is provided with cooling fins.

As a further advantageous concept within the scope of the invention, aclutch may have two or more flywheels, clutch discs and pressure platesarranged in an alternating line-up along the rotational axis of theclutch.

In an advantageous practical embodiment of the foregoing concept, theclutch has one input shaft and two output shafts. The first output shaftruns coaxially inside the hollow second output shaft. The aforementionedalternating line-up, starting from the side of the input shaft,includes:

a first flywheel rotationally fixed on the input shaft;

a first clutch disc rotationally fixed on the first output shaft;

a first pressure plate operable by means of an actuator mechanism toactuate the first clutch disc;

a second flywheel rotationally fixed on the input shaft;

a second clutch disc rotationally fixed on the second output shaft; and

a second pressure plate operable by means of the actuator mechanism toactuate the second clutch disc.

The novel features that are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain presently preferred specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description, examples of embodiments of theinvention are discussed on the basis of the attached drawing in which

FIG. 1 represents a cross-sectional view of a first embodiment of theclutch according to the invention;

FIG. 2 represents a cross-sectional view of a second embodiment of theclutch according to the invention;

FIG. 3 represents a cross-sectional view of a flywheel;

FIG. 4 represents a perspective view of the flywheel;

FIG. 5 represents a cross-sectional view of a motor vehicle clutch.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Unlike the clutch of FIG. 5 that was discussed at the beginning, theclutches that are schematically represented in FIGS. 1 and 2 have twoflywheels, 4 a and 4 b respectively, mounted on the input shaft 2through a rotationally locked connection. Flywheel 4 a cooperates withclutch disc 10 a, pressure plate 14 a, and diaphragm spring 16 a; whileflywheel 4 b cooperates with clutch disc 10 b, pressure plate 14 b, anddiaphragm spring 16 b. The diaphragm springs 4 a, 4 b normally push thepressure plates 14 a, 14 b against the clutch discs 10 a, 10 b, so thatthe latter are pressed into frictional engagement against the respectiveflywheels 4 a, 4 b.

The clutch disc 10 a is mounted through a rotationally locked connectionto an output shaft 8 a, while the clutch disc 10 b is mounted through arotationally locked connection to an output shaft 8 b. The two shaftsrun coaxially, i.e., output shaft 8 b is hollow, and output shaft 8 aextends partially inside output shaft 8 b. Clutches of this type areused, for example, with so-called power-shift transmissions, i.e.,transmissions that can be shifted while transmitting a torque betweenthe engine and the drive train, where the input shaft 2 is coupledsimultaneously or selectively to the output shafts 8 a and 8 b. Theactuator mechanism for actuating the diaphragm springs 16 a, 16 b is notshown in detail, but its principal configuration is analogous to FIG. 5.

When the transmission is shifted while transmitting torque and also whensetting the vehicle in motion from a stand-still condition, a largeamount of heat is generated between the clutch discs and the flywheels.Since the heat is not carried away efficiently by the housing 24, theresultant increase in temperature is known to cause problems.

To improve the removal of heat, all of the radially oriented elements ofthe clutch, i.e., the flywheels, clutch discs, pressure plates anddiaphragm springs are provided with passages 30 (not shown in detail) inthe zone between the outside of the shafts and the inner radius of thefriction linings, so that an air-flow path 32 is cleared next to theoutput shafts 8 a and 8 b. The flywheel 4 a is equipped with fan blades34 and thus functions as a fan that moves air from right to left (inFIG. 1) through the flywheel 4 a. The fan blades could also be pitchedin the opposite sense, so that the air would flow from left to right,i.e., from the flywheel to the bell cover.

Between the housing 24 and the left-facing surface (in FIG. 1) of thefly-wheel 4 a, there is a gap in which the air can flow radiallyoutwards. The air-flow path continues left to right through the gapbetween the peripheral wall 36 of the housing 24 and a cylindrical wall38 that surrounds the clutch parts and connects the flywheels 4 a and 4b. The air flow continues radially inwards on path 40 along theright-hand end surface of the housing. Thus, the air circulates in aclosed loop around the flywheel 4 a and the cylindrical wall 38 andthereby effectively cools the flywheels 4 a and 4 b. As an effectivemeans for transferring the heat from the circulating air stream to theoutside, the interior surface of the housing is provided with coolingfins that are advantageously arranged in those areas where the exteriorsurface of the housing is exposed to the outside air.

It should be clear that the left-facing side of the flywheel 4 a (inFIG. 1) can also have cooling fins in the surface area opposite thering-shaped friction surface. The cooling fins on the flywheel 4 a canperform the additional function of a radial fan to assist in moving theair stream in the outward radial direction.

FIG. 2 illustrates a variant version of the clutch according to theinvention. Reference symbols are shown only for those elements thatdiffer from the embodiment of FIG. 1. In contrast to the substantiallyclosed housing of FIG. 1, the housing 24 of the embodiment of FIG. 2 hasan inlet opening 42 in the area of the right-facing end surface and aring-shaped outlet opening 44 along its outside circumference. Ofcourse, the inlet opening 42, also, can be substantially ring-shaped.

As is immediately evident from FIG. 2, the concept of an inlet 42 andoutlet 44 leads to an air-flow path 50 that does not run in a closedloop. Instead, the air enters through the inlet 42, flows leftward alongthe shafts and passes through the flywheel 4 a, from where it isdirected in the outward radial direction and expelled to the outsidethrough the outlet 44. The embodiment shown in FIG. 2 provides anespecially effective cooling of the clutch.

The flywheel 4 a is shown in cross-section in FIG. 3 and in aperspective view in FIG. 4, omitting the outer cylindrical wall 38 thatconnects the flywheel 4 a with the flywheel 4 b and ends in a radiallyinward bent rim that forms an abutment ring 6 (FIG. 5) for the diaphragmspring 16 b (FIG. 1). The cylindrical wall 38 can, for example, bebolted to the flywheel 4 a, which has fastening holes 46 provided forthis purpose on the circumference of the flywheel 4 a. As illustrated,the flywheel portion that comes into contact with the clutch disc 10 ais configured as a solid ring that carries a friction surface 48 and isjoined to a hub 54 by way of the turbine blades 34. The hub 54 has aninternal tooth profile for a rotationally fixed connection of theflywheel 4 a to the input shaft 2. The turbine blades 34 are shaped sothat the flywheel 4 a functions as an axial fan which, when the enginecrankshaft is running, propels air from right to left (in theillustrated situation) through the openings 30 between the turbineblades 34.

The invention discussed herein on the basis of the illustrated examplescan be modified in a multitude of ways. It is not necessary for theclutch to be of a design with two output shafts. The clutch can beconfigured as shown in FIG. 5, or it can be of a multiple-disc designwhere a plurality of flywheels and clutch discs are arranged to transmittorque between the input shaft and the output shaft. For extremeheavy-duty requirements, the embodiment of FIG. 2 in particular may besupplemented by an electric fan to assist in propelling the air stream,e.g., as a temperature dependent function. It would also be possible todesign both flywheels as axial fans.

To summarize, a clutch of a kind used particularly in the power train ofa motor vehicle has an input shaft 2 carrying one or more flywheels 4 a,4 b constrained to rotate together with the input shaft 2. The clutchfurther has one or more output shafts 8 a, 8 b carrying clutch discs 10a, 10 b constrained to rotate together with the output shafts 8 a, 8 b,respectively. The one or more flywheels 4 a, 4 b have substantiallyring-shaped friction surfaces facing towards corresponding frictionlinings of the one or more clutch discs 10 a, 10 b. One or more pressureplates 14 a, 14 b are axially movable between an engaged and adisengaged position by means of an actuator device 18, 20, 22. In theengaged position, the pressure plate 14 a, 14 b pushes the respectiveclutch disc 10 a, 10 b into friction-locked contact against therespective flywheel 4 a, 4 b, while in the disengaged position, thepressure plate 14 a, 14 b is retracted and the friction lock between therespective clutch disc and flywheel is interrupted. The clutch furtherhas a housing 24 in which the aforementioned parts are accommodated,with openings for the input shaft and the output shaft(s) to passthrough. To provide improved cooling of the clutch, at least oneflywheel (4 a, 4 b) is configured with fan blades 34 at least in a zonethat is radially inside the friction surface, so that the rotation ofthe flywheel will generate an air stream to flow over the surfaceportion of the flywheel on the opposite side from the friction surface.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of theaforedescribed contribution to the art and, therefore, such adaptationsshould and are intended to be comprehended within the meaning and rangeof equivalence of the appended claims.

What is claimed is:
 1. A motor vehicle clutch, comprising: an inputshaft on which a flywheel with a substantially ring-shaped frictionsurface is mounted through a rotationally fixed connection; an outputshaft, on which a clutch disc with a friction lining conforming to andfacing said friction surface is mounted through a rotationally fixedconnection; an axially movable pressure plate; an actuator device thatserves to move the pressure plate between an engaged position in whichthe pressure plate is urging the clutch disc into friction-lockedcompressive contact against the flywheel and a disengaged position inwhich the pressure plate is retracted and the friction-lockedcompressive contact is interrupted; and a housing with openings for theinput shaft and the output shaft to pass through; wherein fan blades areintegrally formed in the flywheel, said fan blades being arranged atleast adjacent to an inner radius of the friction surface andsubstantially axially abreast with the friction surface, so that therotation of the flywheel will cause a radially outward-directed airstream to flow on the side of the flywheel that faces away from thefriction surface.
 2. The clutch of claim 1, wherein the flywheel, theclutch disc and the pressure plate in a radial zone between the outputshaft and the inner radius of the friction surface are equipped with airpassages allowing the air stream to flow axially along the output shaft.3. The clutch of claim 2, wherein the housing surrounds the flywheel,the clutch disc and the pressure plate in an arrangement that provides aclosed-loop circulation path for the air stream, said path running in anaxial direction along the output shaft from the pressure plate to theflywheel, then turning radially outwards and continuing in a radialdirection between the housing and the flywheel, then turning into andcontinuing in an axial direction along a peripheral housing wall fromthe flywheel to the pressure plate, then turning into and continuing inan inward radial direction to complete the closed-loop circulation path.4. The clutch of claim 2, wherein the housing has an air inlet and anair outlet, and an air flow path leads through the housing, said airflow path running from the air inlet through the flywheel to the airoutlet.
 5. The clutch of claim 4, wherein the air inlet is located onthe side of the housing that is farther away from the flywheel and theair outlet is located in a peripheral housing wall, so that the air flowpath runs in an axial direction from the air inlet along the outputshaft, passes through the flywheel, then turns into and continues in anoutward radial direction between the housing and the flywheel to the airoutlet.
 6. The clutch of claim 1, wherein the housing has an interiorsurface that is provided with cooling fins.
 7. The clutch of claim 1,wherein the flywheel performs the function of an engine flywheel.
 8. Theclutch of claim 1, wherein the flywheel is provided with cooling fins.9. The clutch of claim 1, wherein the flywheel, the clutch disc and thepressure plate form a first functional group, and wherein the clutchcomprises at least one further functional group having a furtherflywheel, a further clutch disc and a further pressure plate, said firstfunctional group and the at least one further functional group beingarranged in an axially stacked sequence of functional groups.
 10. Theclutch of claim 9, wherein the at least one further functional group isa second functional group comprising a second output shaft, the furtherflywheel is a second flywheel, the further clutch disc is a secondclutch disc, and the further pressure plate is a second pressure plate,wherein the second output shaft is hollow and the output shaft runscoaxially inside the second output shaft, wherein the second flywheel isrotationally fixed on the input shaft, the second clutch disc isrotationally fixed on the second output shaft; and the second pressureplate is operable by means of the actuator mechanism to actuate thesecond clutch disc.